CBSE Questions for Class 12 Medical Physics Semiconductor Electronics: Materials, Devices And Simple Circuits Quiz 6 - MCQExams.com

In a semiconductor, which of the following statement is correct?
  • At $$0 K$$, Si is a super conductor.
  • In a p-type semiconductor the acceptor level lies near the conduction band.
  • Each donor atom contributes one hole.
  • p - n junction is electrically neutral.
In an n-p-n transistor circuit, the collector current is $$10mA$$. If $$90\%$$ of the electrons emitted reach the collector, then
  • the emitter current , the will be $$9mA$$
  • the base current will be $$1 mA$$
  • the emitter current will be $$11.11 mA$$
  • The base current will be $$1.11 mA$$
A zener diode, having breakdown voltage equal to $$15 V,$$ is used in a voltage regulator circuit shown in figure. The current through the diode is :
68614_d571f2b033a0467e9c433d560b93bb6c.png
  • $$5 mA$$
  • $$10 mA$$
  • $$15 mA$$
  • $$20 mA$$
A pn photo diode is fabricated from a semiconductor with a band gap of 2.5 eV. It can detect a signal of wavelength :
  • $$496A^o$$
  • $$6000A^o$$
  • 4000 nm
  • 6000 nm
Statement-1: NOT gate is also called invertor circuit.
Statement-2: NOT gate inverts the input order.
  • Statement -1 is false, statement -2 is true.
  • Statement 1-is true, statement -2 is true and statement -2 is correct explanation of statement-1.
  • Statement 1-is true, statement -2 is true but statement -2 is not correct explanation of statement-1.
  • Statement 1-is true, statement -2 is false.
Statement-1: Two semi conductors of p and n type  form p-n junction which act like a rectifier.
Statement-2: A rectifier is used to convert alternating current into direct current.
  • Statement -1 is false, statement -2 is true
  • statement 1-is true statement -2 is true statement -2 is correct explanation of statement-1.
  • statement 1-is true statement -2 is true statement -2 is not correct explanation of statement-1.
  • statement 1-is true statement -2 is false
Following diagram performs the logic function of :
69509.PNG
  • AND gate
  • NAND gate
  • OR gate
  • XOR gate

Match List-1 with list-2

 List-1 List-2
 A. Emitter E. Transistor
 B. Base F. Moderately doped
 C. Collector G. Lightly doped
 D. Transfer of resistance H. Heavily doped

 I. largest physical size
  • A-F B-E C-H,I D-G
  • A-G B-F,I C-E D-H
  • A-H B-G C-F,I D-E
  • A-E B-H,I C-G D-F
Following truth table represent which logic gate :
ABC
110
011
101
001
  • XOR
  • NOT
  • NAND
  • AND
Absence of electron in a valence band of semiconductor is called
  • Electron
  • Positron
  • Holes
  • Valence
A storage battery takes $$t_0$$ time when $$DC$$ current $$I_0$$ is used to charge it. Find the time taken if a half wave rectifier is used with $$AC$$ mains and effective current is $$I_0$$.
  • $$\displaystyle t_0 \pi$$
  • $$\displaystyle \dfrac{2t_0}{\pi}$$
  • $$\displaystyle \dfrac{\pi t_0}{2}$$
  • $$\displaystyle t_0$$
Which of the following is a semi-conductor ?
  • Constantan
  • Porcelain
  • Germanium
  • Silicon
Semiconductor without any impurities are
  • Intrinsic Semiconductor
  • Extrinsic Semiconductor
  • Both (a) and (b)
  • None of these
When a small quantity of donor impurity is added to pure semiconductor, then resulting semiconductor is
  • n - type
  • p-type
  • p-n-type
  • None of these
When a P - N junction is unbiased, the junction current at equilibrium is :
  • zero as no charges cross the junctions
  • zero as equal number of charge carriers cross the barrier in opposite directions
  • mainly due to diffusion of majority charge carriers
  • mainly due to diffusion of minority charge carriers
Alternating current is converted to direct current by
  • rectifier
  • dynamo
  • transformer
  • motor
Semi conductor in pure form is ........................... semiconductor.
  • Intrinsic
  • Extrinsic
  • Real
  • None of these
A transistor based radio receiver set (effective resistance of the order of 18 ohms) operates on a 9V (dc) battery. If this battery is replaced by a dc power supply with rating 9V, 500A then
  • receiver will work normally
  • receiver will give distorted output
  • receiver will get burnt
  • power supply will get over heated
In P-N junction diode offers high resistance in ................. condition.
  • Forward bias
  • Inverse bias
  • Reverse bias
  • None of these
A semiconductor at $$0^{\circ}K$$ is
  • Unstable
  • Stable
  • Neutral
  • Forward biased
A laser operates at a frequency of $$3\times 10^{14} H_z$$ and has an aperture of $$1cm$$. The radii spread of the beam is 
  • $$10^{-3}$$ radian
  • $$5\times 10^{-3}$$ radian
  • $$10^{-4}$$ radian
  • $$10^{-2}$$ radian
A junction transistor does not have _________.
  • Emitter-base junction
  • Base-collector junction
  • Emitter-collector junction
  • None of the above
In the circuit shown, the diode is ideal. The potential of $$A$$ is higher than the potential of $$B$$. If the switch $$S$$ is $$(i)$$ closed$$, (ii)$$ open the equivalent resistance between $$A$$ and $$B$$ is

151996.png
  • $$R, R$$
  • $$\dfrac{R}{2}, \dfrac{R}{2}$$
  • $$\dfrac{R}{3}, \dfrac{R}{4}$$
  • $$\dfrac{R}{4}, \dfrac{R}{3}$$
To achieve DC from AC, AC be applied across :

153532_eb39389ffa6d4ddca8a524b6f73f6763.png
  • BD
  • AC
  • BC
  • CD
  • AD
Light produced by LASER is
  • monochromatic but not coherent.
  • monochromatic and coherent.
  • coherent but not monochromatic
  • neither coherent nor monochromatic
The free electron density is more in .....
  • Conductors
  • Insulators
  • Semi conductors
  • Electrolytes
The band structure determines the conductive behaviour of a solid.
  • True
  • False
A three dimensional photographs of an object is obtained using
  • spectrography
  • holography
  • photography
  • shadow photography
Which of the following sources gives best monochromic light?
  • A candle
  • A bulb
  • A mercury tube
  • A laser
Wavelength of a laser beam can be used as a standard of:
  • time
  • temperature
  • angle
  • length
A sinusoidal voltage of peak value $$200 V$$ is connected to a diode and resistor $$R$$ in the circuit shown so that halfwave rectification occurs. If the forward resistance of the diode is negligible compared to it, the r.m.s. voltage (in volt) across $$R$$ is approximately
210885_41fccf41e78e47299a7a6c02e26ae810.png
  • $$200$$
  • $$100$$
  • $$\displaystyle \dfrac{200}{\sqrt 2}$$
  • $$280$$
In bridge rectifier circuit, (see fig.), the input signal should be connected between
210887_4a2174737a5846cd9212b0574ff138e4.png
  • A and D
  • B and C
  • A and C
  • B and D
In a transistor
  • the emitter has the least concentration of impurity
  • the collector has the least concentration of impurity
  • the base has the least concentration of impurity
  • all the three regions have equal concentrations of impurity
The average value of output direct current in a full wave rectifier is
  • $$I_0/\pi$$
  • $$I_0/2$$
  • $$\pi I_0/2$$
  • $$2I_0/\pi$$
Negative feed back
  • increases stability
  • decreases stability
  • produces oscillation
  • stops current in the tube
In a full wave rectifier circuit operating from $$50 Hz$$ mains frequency, the fundamental frequency in the ripple would be
  • $$25 Hz$$
  • $$50Hz$$
  • $$70.7 Hz$$
  • $$100 Hz$$
In the half wave rectifier circuit operating from $$50 Hz$$ mains frequency, the fundamental frequency in the ripple would be
  • $$25 Hz$$
  • $$50 Hz$$
  • $$70.7 Hz$$
  • $$100 Hz$$
A transistor has $$\beta$$ =A change in base current of 100 $$\mu$$ A, produces change in collector current
  • $$40 \times 100 mA$$
  • $$(100-40) mA$$
  • $$(100+40) mA$$
  • $$100/40 mA$$
To which logic gate does the truth table given below correspond?
ABY
000
011
101
110
  • AND gate
  • NAND gate
  • NOR gate
  • XOR gate
The truth-table given below is for which gate?
ABC
001
011
101
110
  • XOR
  • OR
  • AND
  • NAND
What is the value of $$A. \bar{A}$$ in Boolean algebra?
  • $$0$$
  • $$1$$
  • $$A$$
  • $$\bar{A}$$
To which logic gate does the truth table given below correspond?
ABY
000
100
000
111
  • OR gate
  • AND gate
  • NAND gate
  • NOR gate
In a common base amplifier the phase difference between the input signal voltage and the output voltage is
  • 0
  • $$\pi/4$$
  • $$\pi/2$$
  • $$\pi$$
To which logic gate does the truth table given below correspond?
ABY
001
101
011
110
  • OR gate
  • AND gate
  • NAND gate
  • NOR gate
In the following circuit, the output Y for all possible inputs A and B is expressed by the truth table.
211265.jpg
If the ratio of the concentration of electrons to that of holes in a semiconductor is $$\displaystyle \frac{7}{5}$$ and the ratio of current is $$\displaystyle \frac{7}{4}$$, then what is the ratio of their drift velocities?
  • $$\displaystyle \frac{5}{8}$$
  • $$\displaystyle \frac{4}{5}$$
  • $$\displaystyle \frac{5}{4}$$
  • $$\displaystyle \frac{4}{7}$$
In a bridge rectifier, the number of diodes required is
  • $$1$$
  • $$2$$
  • $$3$$
  • $$4$$
The truth table given below is
ABY
001
011
101
110
  • NOR
  • AND
  • XOR
  • NAND
The cause of the potential barrier in a p-n diode is
  • depletion of positive charges near the junction
  • concentration of positive charges near the junction
  • depletion of negative charges near the junction
  • concentration of positive and negative charges near the junction
Which of the following represents NAND gate ?
0:0:1


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